High quality animal blood is a source of valuable protein additives for use in the food industry. Powdered red blood cells (RBC) from pigs and cattle have been used to make dark breads in Europe and in pet foods. In addition, powdered plasma protein because of its functional properties has been used as a protein additive in meat and confectionery products.
At the present time, the blood which is used to prepare protein additives is collected in slaughterhouses, a solution of sodium citrate is added to the blood as an anticoagulant, and, the blood is separated by centrifugation or other means into its RBC and plasma protein fractions. The resulting fractions are concentrated or purified, if desired, to food grade standards by use of reverse osmosis or other conventional protein purification techniques.
The use of sodium citrate solutions as anticoagulants is not without disadvantages. One disadvantage is that the concentrations of sodium citrate which must be used are relatively high (6 to 8% by weight) and result in significant ash. Another disadvantage is that the separation of blood which has been treated with a conventional sodium citrate solution, into its protein fractions, tends to foul the separation and purification equipment.
It obviously would be advantageous to have better anticoagulants and methods for treating blood than those presently used.